The present invention relates to a zigzag folding apparatus utilized in a form printing machine for folding a paper form strip, primarily provided with perforated lines formed in a processing section of the machine after printing, in a zigzag along the perforated lines arranged transversely therein.
In FIG. 13, a form printing machine in the complete arrangement is shown which is utilized for printing paper forms such as computor oriented business forms or the like. The letter A is a paper infeed section for feeding a strip of rolled paper P while the letter B is a printing section having a plurality of printing units B1 for performing offset printing on the paper strip P infed. Then, the paper strip P printed is transffered from the section B through a processing section, in which punching and lengthwise and widthwise perforating operations are carried out, finally to a paper exit section D. The paper exit section D includes the zigzag folding apparatus D1 in which the paper strip P printed and processed is folded consecutively in a zigzag along the transverse perforated lines formed therein.
A known arrangement of the zigzag folding apparatus D1 will be described as best shown in FIGS. 11 and 12.
The numeral 1 is a folding arm which is rotatably supported at the upper end thereof by a horizontal shaft 2 thus to move about the horizontal shaft 2 (which will be termed an arm-center shaft below) in rightward and leftward swing motion, as represented by the arrow mark A, through the movements of a crack shaft mechanism unshown. The folding arm 1 has at lower end a swing lever 3 and a pair of paper outfeed rolls 4 and 5 mounted thereto. The two rolls 4 and 5 (which will be termed left and right rolls according to the directions in the illustrations) are rotatably mounted to their respective axles 6 and 7 attached to the swing lever 3. Upon being fed outwardly between the two rolls 4 and 5 rotating in opposite directions, the paper strip is folded in a zigzag by the rightward and leftward swing movements of the arms 1.
The swing lever 3 swings rightwards and leftwards about the center-axle 6 (which will be termed a lever-center axle) of the left roll 4, as represented by the arrow B, through the reciprocating movements of a crank mechanism 8. By the swing movements of the swing lever 3, the right roll 5 is moved in swing motion about the center-axle 6 of the left roll 6 so as to assist the folding arm 1 in its paper folding operation (as will be temed an auxiliary folding operation hereinafter).
As shown in FIG. 12, a drive pulley 9 driven by a motor unshown is mounted to the arm-center shaft 2 while an idle pulley 10 is mounted to the lever-center axis 6, between which pulleys a belt 11 is fitted. These members form a roll rotating mechanism which drives both the rolls 4 and 5 for rotation. As shown in both the illustrations, the numeral 12 is a guide member for outfeeding the paper strip.
Disadvantages in the aforesaid known arrangement are, as follows.
(I) As the right roll 5 moves in the swing motions against the left roll 4 fixed in position during the auxiliary folding operation, the point of contact C between both the rolls 4, 5, as a paper outfeeding point, changes its position constantly, which results in an intensive force such as tension exerted on the paper strip. Particularly, while a swing angle is great as needed, a rate of the position change becomes increased thus to affect the paper strip greatly.
(II) Since the small-diameter left roll 4 is directly driven for rotation by the belt drive roll rotating mechanism, the proximal region of the left roll 4 is affected greatly. In case that the proximal area of the left roll 4 are reinforced in construction, the lower portion of the folding arms 1 becomes heavier, which increases the force of inertia on the folding arm 1 and therefore, will shorten the life of a folding arm mechanism, etc.
To solve the problem about the auxiliary folding operation described above in (I), the contact point C between the two rolls 4 and 5 can be equal in position to the swing center of the swing lever 3. However, although this permits the roll contact point C to rest in position, the distance between the pulleys in the roll rotating arrangement varies as the left roll 4 swings about the contact point C, which then requires an additional mechanical arrangement in which the length of the pulley belt can be changed automatically in accordance with the auxiliary folding operation. Consequently, this develops another problem that the arrangement becomes intricate in construction.
Additionally, the known zigzag folding apparatus D1 has a swing section including the paper outfeed guiding device pivotably mounted to the lower end of the folding arm which swings about the axis in the upper end thereof. The folding arms and paper outfeed guiding device are activated by their respective crank mechanisms for the swing movements in the arrangement so that the paper strip passed through the paper outfeed guiding device can be folded in a zigzag along the transversely perforated lines arranged therein.
According to the arrangement, in order to alter the swing angle (which will be termed a width of swing stroke) in the swing section in accordance with the locations (folding positions) of the transversely perforated lines, an eccentric crank is displaced in relation to a rotary disk in the crank arrangement thus to change the eccentiricity or the length of the swing stroke. This adjustment can be done while the machine remains rested, which interrupts the folding operation and therefore, will result in a decrease in working efficiency.
It is apparent that the present invention intends to solve the aforesaid problems.
It is an object of the present invention to provide a zigzag folding apparatus for a form printing machine wherein the distance between the drive and idle pulleys in the roll rotating arrangement can remain constant while the point of contact between a pair of the rolls coincides approximately with the swing center of the swing lever and furthermore, no unnecessary load is exerted on the proximal area of the primary roll.
It is another object of the present invention to provide a zigzag folding apparatus for a form printing machine wherein the adjustment on a width of the swing stroke at the swing section can be made without stopping the machine.
The further objects and advantages of the invention will be apparent from the following description.